304 Mr Philip Sewoll on tJie [se ^s. lh. 



of vegetation, the striking fact mentioned by Darwin of a 

 double yellow hollyhock which, one year, suddenly turned 

 into a pure single white kind, and in which subsequently 

 a branch bearing the original double yellow flowers re- 

 appeared among the other branches. 



Or, in conclusion, to take a yet more interesting case, it is 

 recorded by Darwin in the same work, — Variation under 

 Domestication, — that "white tubers of potato may be obtained 

 from purple varieties by planting eyes which have so varied. 

 A plant in Lancashire, of Kemp's potato, which is properly 

 white, produced two "tubers which were red. The red kind 

 was propagated in the usual manner, and kept true to its 

 new colour, and, being found a more prtxluctive variety, soon 

 became known as " Taylor's Forty-fold." 



Sach examples as these last, and many of the preceding, 

 sliould enable us to judge with increasing precision, although 

 it may still be with indistinctness, as to the meaning of 

 colour physiologically, not merely its meaning with relation 

 to insects, the only part of the plant-environment to which 

 it has so far been clearly shown to be related. 



It will be seen that I have gathered together references 

 to a considerable number of recent pamphlets, of which the 

 main facts are incorporated in my paper ; but as the list of 

 papers includes all those which have been reviewed in English 

 science reviews within the last ten years, it is probable that 

 most if not all of importance, of later date than the papers 

 mentioned in Professor Vines' Lectures on Physiology, will 

 be included in the lists. They do not profess to be perfect 

 reference lists to recent literjiture, they are essentially those 

 troiii whicli this paper has been compiled. 



In referring to some of this recent literature, it is very far 

 indeed from my wish to undervalue any of those popular 

 works inentioiicd, wliicli liavc, in so excellent a manner, 

 delighted a very large nundjer of readers. I can only con- 

 fess that, from the present standjooint, tliese works appear 

 to me to have dealt very inadequately with causes of colour- 

 variation, and to have given to the inihicnce of selection 

 Ijy insects, the use of it, a somewliat undiu; ])rominence. 



The fact that the present paper is an outcome of the one 

 on " Floral Colour," written l)y me in conjunction with Mr 

 Geddes, in wliich the inlluence of natural selection was 



